This is a phase III, double blind, randomized, placebo controlled, multicenter, multidose study. Subjects will be randomized to received rhIGF-I or placebo at a dose of 10, 20, or 40 ug/kg SC BID as co-therapy with insulin. Approximately 1400 male and female (ages 8-75 y.o) with Type 1 diabetes mellitus currently receiving two or more injections of insulin per day will be enrolled. The study consists of three periods: 1) Screening period not to exceed 4 weeks prior to pretreatment 2) a 2-week pretreatment period and 3) a 48 week treatment period. During the pretreatment period, subjects will be given a One-Touch Profile BG meter and instructed to monitor their BG four times daily. On day 1, subjects will be instructed to alter their daily insulin dose in order to achieve protocol defined targets of glucose levels. In order to avoid hypoglycemia and other adverse events associated with rapid improvement in glucose control, the study is also designed to use an escalation in the dosing level of rhIGF-I. It is anticipated that escalating the dose slowly will diminish the incidence of these adverse events.